Sense of smell linked to memory and emotion
My girlfriend from school used to wear a perfume called "Anais Anais". The other day, I was passing someone at a shopping mall when I smelled it...
Then, memories of more than 30 years ago suddenly come back to me, and I feel sweet and sad. This phenomenon of reviving dormant memories with odors is called the “Proust Effect”. It is known that the sense of smell is closely linked to memory and emotion, even among the five senses of human beings.
The five human senses do not function independently. They are unconsciously cross-modalities (multisensory integration that exchanges information with each other). Based on this fact, the Association
When olfactory receptors in the nasal cavity catch odor molecules, the signals pass through the olfactory bulb and then through the limbic system (entorhinal cortex, amygdala, hippocampus, hypothalamus) before reaching the orbitofrontal cortex, which is responsible for multisensory integration.
On the other hand, all of the reciprocal senses (sight, hearing, taste, and touch), with the exception of smell, always pass through the thalamus before reaching their respective cortices, making the neural circuits complex and time-consuming until they reach the limbic system.
However, as mentioned above, only the sense of smell enters the limbic system directly, so memory and emotion are stimulated prior to the perception of "what is this smell?
In other words, smells are characterized by the fact that they instantly jolt memories and emotions before they can be reasoned with. At the same time, the hypothalamus is stimulated, which affects various physiological functions such as excitement, sedation, concentration, sleep, and stress via the autonomic nervous system.
As will be explained later, it has been found that complete loss of the sense of smell is associated with increased subsequent mortality. In surveys asking, "Which of the reciprocal senses would you not want to lose? Smell is usually ranked at the bottom of the list, but it is in fact a very important sense for the human body.
Olfaction from the Evolution of Sensory Receptor Genes
How many odorants exist in the world? It is not known for sure, but it is estimated to be several hundred thousand.
We are surrounded by a wide variety of plant, animal, food, and body odors, most of which are mixtures of hundreds of odorants. The ability to distinguish between these myriad odors has a major impact on the survival strategies of animals.
There are some interesting facts in the evolution of genes involved in human reciprocity. For example, "bitterness" is essential for judging poisonous substances. The pheromone system (paranasal olfactory system) has degenerated as well.
Mammals, which were forced to be nocturnal during the heyday of the dinosaurs, developed an unusual sense of smell while their sense of color degenerated.
In the subsequent evolutionary process, some primates (including humans) that turned diurnal regained their color vision once lost and trichromatic vision (red, green, and blue color opsin genes) was restored, while olfaction degenerated (about half of the human olfactory genes were replaced by pseudogenes, i.e. lost function), but ....
In fact, even after subtracting these genes, the number of olfactory genes is still far greater than the number of visual genes. While there are only a few sensory receptor genes involved in human color vision, about 400 have been found for olfaction (more than 800 in total if pseudogenes are included).
When we look at the evolutionary phylogenetic tree, it is clear how long olfactory dominance has existed in the history of evolution, considering that the broad-nosed monkeys, which lack trichromatic vision, branched out about 80 million years ago, and the narrow-nosed monkeys, which can see three colors, about 40 million years ago, and mammals were born 225 million years ago before that.
In other words, it is no exaggeration to say that the evolution of mammals is "a history of seeing the world through smells. That is why we can say that there is a strong connection with memory and emotion.
Humans, at the pinnacle of biological evolution, have now developed the cerebral cortex and dramatically improved our ability to memorize and transfer knowledge, which has led to a lower evaluation (relative value) of the sense of smell.
Just like the brain map of the somatosensory cortex, there's a "smell map"!
CC view 2.5 https://commons.wikimedia.org/wiki/File:Head_olfactory_nerve_-_olfactory_bulb_ja.jpg (some of the images have been processed)
As shown in the figure above, the olfactory sensing mechanism is a one-to-one correspondence between glomeruli that receive axonal projections from olfactory cells that capture odorant substances (substrate). The two-dimensional depiction of the glomeruli on the surface of the olfactory bulb (see the figure below) is input to the brain, which then recognizes the odor as "what is the odor? This image information is then input to the brain, which generates the perception of "what is that smell?
It is as if the brain recognizes smells in the same way as the brain map of the somatosensory cortex. This mechanism seems to confirm the validity of the previous statement that "mammals have seen the world through smells throughout their evolutionary history.
Mutant mice not afraid of cats
By comparing mice in which the upper half of the olfactory bulb's odor map was destroyed with mice in which the lower half was destroyed (experiments with genetically engineered knockout mice), we found something very interesting.
It was found that there are two cognitive pathways for odor: an instinctive circuit and a learned circuit, both of which reach the central nervous system in parallel.
In other words, for animals, the brain makes judgments (pleasant or unpleasant) about a smell by matching the results of these two inputs: an instinctive circuit that senses whether the smell is dangerous, such as the smell of wildfire or natural enemies, and a learned circuit that makes judgments based on acquired empirical rules.
Knockout mice in which only the instinctive circuits have been destroyed will no longer fear natural enemies and will show abnormalities in their reproductive and brood-rearing behavior. They no longer run away when confronted with a cat (however, their learning circuits are normal, so there is no problem with their ability to distinguish smells, and they can tell the difference between faint odors).
Furthermore, if the mutant mice are fed sugar at the same time as the natural enemy odor, they will eventually perceive the natural enemy odor as a "good smell" and come close to the mutant mice. In the case of cats, this means that the mice will become attracted to cats.
It is now known that such twisting of instinctive and learned circuits can actually occur even in normal animals. In some cases, the instinctive circuit tells the animal to "run away," while the learned circuit tells the animal to "come closer. In fact, this is what lies at the root of Smell Harassment.
As will be explained later, some of the chemicals in fabric softeners contain molecular structures that organisms should instinctively avoid. Imagine this. How would Paleolithic humans react if they smelled the strong odor of fabric softener?
Do you think that they, with their "healthy" instinctive circuits that have not degenerated like modern humans, would find the smell as "nice" as we do?
The same thing that happens with taste disorders caused by excessive intake of refined sugar and food additives may in fact be happening with the sense of smell as well. In the near future, judgments of "pleasure" in fabric softener scents may be positioned as being similar to "olfactory impairment.
Nioi and the Japanese
While perfume is not a problem in the dining scene of heavily seasoned foreign cuisine, it is a no-no in Japanese cuisine, which emphasizes the gentle aroma and delicate "umami" of its ingredients. Historically speaking, Japanese people are sensitive to smells.
It is said that in the 17~18th century, Edo was the most hygienic megacity on the planet. And now, Japan is the country that sells the most antibacterial goods and deodorizers in the world.
Traditionally, the Japanese are not fond of strong odors and have a high sense of hygiene, preferring cleanliness. In fact, this national character is a double-edged sword.This articleAs explained in the following section, it is next to the risk of mask addiction....
If taken to excess, such lifestyle habits as thorough sterilization and deodorization can lead to obsessive-compulsiveness and addiction. It must be said that the tendency to avoid or be hostile to odors derived from vital activities such as sweat and body odor, or in other words, odors that indicate human existence, is extremely dangerous.
In a blind test for age-related odors, many people respond that they "neither like nor dislike" the smell, but as soon as it is associated with "uncle's or father's smell," they find it "unpleasant," which is truly a cognitive distortion....
The effects of smell on brain activation and dementia are becoming common knowledge in recent cognitive science, but excessive odor countermeasures seem to be an attempt to eliminate smell from society.... But what would happen to humans if smells were really eliminated?
An American research group found that "complete loss of the sense of smell results in a higher rate of death within five years than any other disease.
We know that the loss of the sense of smell exposes many humans to very high levels of stress. At the same time, they experience an unexplainable sense of anxiety.
This is rooted in the primate evolutionary survival strategy of grouping, or the acquisition of collectivity. The grooming, touching, and
Humans communicate non-verbally by sensing each other's smells subconsciously, in other words, "exchanging information on smells. This is what we are trying to do.
The reason why the Society emphasizes touching in general clinical practice and why we warn against mask addiction can be likened to the above (primate evolutionary process).
When a father comes home late at night after a long day at work, he wants to hug his sleeping child because the smell of his own child gives him an incomparable sense of security.
Identity of fabric softener odor
Manufacturers, having taken notice of the fastidiousness of the Japanese people, engaged in fierce sales competition for antibacterial, deodorizing, and fragrance-related goods, and through the overwhelming influence of TV commercials, established a huge odor business (market) that could be called a fragrance revolution.
A major role in this was the revolutionary technology to make the fragrance last longer."
The fragrance and deodorant components are trapped in microcapsules made of urethane or melamine resin, and the microcapsules adhering to the clothing break down after a time lag due to friction, etc., so that the fragrance lasts for an extended period of time.
Various studies have reported problems caused by the diffusion of broken microcapsule materials such as synthetic resin monomers, deodorant ingredients, fragrances, and microplastic fragments into the air, as well as health hazards caused by inhalation of these man-made chemicals, and it is almost certain that they cause chemical sensitivity. It is considered almost certain that they cause chemical sensitivity.
BReINFor those who are constitutionally at risk for chemical sensitivity, or who have already developed it, scent pollution is already a "crisis that is there now.
BReIN
Research is also being conducted on the relationship between aroma pollution and allergy symptoms, and the Ministry of Health, Labor and Welfare and other municipalities (local governments) have begun to raise awareness of aroma pollution - with warnings on their official websites.
BReINThe reality is that an overwhelming number of manufacturers prioritize their own profits over people's health, despite the fact that the number of patients actually suffering from fragrance damage is increasing.
Some companies have begun to change their microcapsules to safer materials, while others are trying to further strengthen the traditional line of "more capsules adsorbed on the clothes to keep the fragrance longer....
There is only one way to change a company's stance. It is a change in awareness on the part of consumers. I believe this is the only way. We should not buy such products. If they don't sell, companies will change their stance and shift to developing safer products.
There is no effective way to achieve this other than to increase the number of people who are aware of the various potential problems associated with excessive fabric softener odors by increasing the number of people who know the content of this article, "The Cognitive Science of Odors.
Smell stimulates human emotions and is prone to cognitive distortions, causing the brain to feel a false sense of pleasure in response to artificial chemicals that the body does not naturally desire. The brain is at risk of gradual breakdown due to a mechanism that is not unlike drug addiction.
A father who is tired from work should instinctively want the smell of his children, not the chemicals released from the microcapsules.
And yet, it is nothing short of tragic that the artificial smells sinking into the child's pajamas are taking over the father's olfactory bulb map. He will not be able to detect changes in his child's physical condition, and his own sensory processing will deteriorate, and he will lose the ability to discern and smell what is good for him, increasing his risk of developing dementia in the future.
What danger does an activity that destroys smelling, which is an instinct of animals, pose to the future of humanity? How important is it to set up an environment that takes human smelling into consideration when we move to Mars?
Japanese society should not underestimate the delicacy of the human sense of smell. We should keep in mind that excessive fastidiousness will never light up the future of Japan.
I personally feel that the human brain, which is attracted to the smell of fabric softener, is not much different from the brain of a mutant mouse that is not afraid of cats...but maybe I am being a little too perverse. What do you think?
◆National Consumer Affairs Center of Japan (Providing information on the smell of fabric softener)
BReINhttps://www.kokusen.go.jp/news/data/n-20130919_1.html
◆NPO Chemical Sensitivity Support Center (general knowledge and consultation on chemical sensitivity and other concerns)
BReINhttps://cssc4188cs.org/free/soudan
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